Speedometer problem

[DaveK]

Hi everyone

Noticed a rather strange feature on my speedometer while driving at the weekend.

When I started driving, the speed reading was very low - not even close to what I knew I was driving at. If I took my foot of the throttle briefly the speed would jump up to what I figured was the right speed but if I put my foot back on the gas it dropped again.

After driving about 10km or so it seemed to get back 'in sync' with the speed I was at. (When it warmed up I guess?).

Tried it again the next day and had the same issue. Can anyone shed any light on the possible cause and solution?

Thanks

[GOLDCYLON]

Hi everyone

Noticed a rather strange feature on my speedometer while driving at the weekend.

When I started driving, the speed reading was very low - not even close to what I knew I was driving at. If I took my foot of the throttle briefly the speed would jump up to what I figured was the right speed but if I put my foot back on the gas it dropped again.

After driving about 10km or so it seemed to get back 'in sync' with the speed I was at. (When it warmed up I guess?).

Tried it again the next day and had the same issue. Can anyone shed any light on the possible cause and solution?

Thanks

Sounds like an issue with the variable speed sensor. Are your running stock gears?

[DaveK]

Sounds like an issue with the variable speed sensor. Are your running stock gears?

I have 4.10s in at the moment, VSS correction gear from Marc H.

[tccrab]

First thing I'd check is to crawl under the car and see if the connector to the speed sensor on the transmission is on tight and not corroded.
Then I'd check the plugs on the ECM as the speedo output to the dash comes from there.

TomC
"Crabs"

[Jeffvette]

Dave any other unusual things displaying on the cluster?

[GOLDCYLON]

First thing I'd check is to crawl under the car and see if the connector to the speed sensor on the transmission is on tight and not corroded.
Then I'd check the plugs on the ECM as the speedo output to the dash comes from there.

TomC
"Crabs"

Yeah Tom thats where I was going and why I asked about the gears. I also learned about the 3-4 inputs that feed the VSS and the cycle count when installing the Nav system in the car. So my money was on a 4.10s setup with a speed sensor device. Damn Im learning a lot about this car lol. GC Good luck

[DaveK]

Dave any other unusual things displaying on the cluster?

No Jeff. Everything looks absolutely fine. Just the speed number is wrong. I don't see any random pixels or anything that might suggest the display itself was failing.

[DaveK]

First thing I'd check is to crawl under the car and see if the connector to the speed sensor on the transmission is on tight and not corroded.
Then I'd check the plugs on the ECM as the speedo output to the dash comes from there.

TomC
"Crabs"

I'll try checking those. Thanks Tom

[Jeffvette]

No Jeff. Everything looks absolutely fine. Just the speed number is wrong. I don't see any random pixels or anything that might suggest the display itself was failing.


On the AC unit, before you start moving, hold the fan speed up and down buttonsn at the same time for 5-7 seconds, release, use the fan speed up button to go -07- and hit the auto button. That will give you the speed reading. See if it corresponds with what you are getting on the cluster.

[FU]

Dave any other unusual things displaying on the cluster?

Yea....a image of your avatar :p

[GOLDCYLON]

Yea....a image of your avatar :p

If only ;)

[DaveK]

On the AC unit, before you start moving, hold the fan speed up and down buttonsn at the same time for 5-7 seconds, release, use the fan speed up button to go -07- and hit the auto button. That will give you the speed reading. See if it corresponds with what you are getting on the cluster.

I'll try that too. Thanks

[DaveK]

I tried the trick with the AC Unit display and it reads the same as the main display. So I'm guessing that eliminates possible display and is more likely related to the VSS itself. Does that sound right?

Thanks

p.s. that's a neat trick with the AC display - is there a list of information you can get out of that somewhere? I imagine there's a whole load of diagnostic info available.

[Jeffvette]

I tried the trick with the AC Unit display and it reads the same as the main display. So I'm guessing that eliminates possible display and is more likely related to the VSS itself. Does that sound right?

Thanks

p.s. that's a neat trick with the AC display - is there a list of information you can get out of that somewhere? I imagine there's a whole load of diagnostic info available.

You got it. There is some other stuff, but the only thing worth mentioning is the coolant readout. code -16-

What fluid are you running in the trans?

Get under spray the area with some brake kleen, pull the connector off, spray out with some electrical contact cleaner.

Have you done anything with the stereo? SCV working correctly, cruise control operational?

[DaveK]

Just checked the connectors to the ECM and they all seem tight. Going to try and get to the underneath but I have limited access so not sure I will be able to get to it (no garage at the moment and gravel drive so I'm on ramps) - I had to take it to a shop to get the VSS gear installed.

Haven't done anyting to the stereo, SCV and cruise seem fine too. Not sure of the transmission fluid - it was from my local GM dealer and for the ZF gearbox.

[DaveK]

Just wanted to put an update here for anyone searching - taken me a while but finally managed to get underneath the car with some help from another vette buddy 'loaning' me his garage.

As mentioned, previously I had a problem with the speedometer reading 0 for the first 10 minutes or so, then as it warmed it would show semi-random numbers until it finally got to the point where it was reading true.

I figured it must be the something to do with the VSS and this week managed to finally inspect it. The connections looked okay so that didnt seem to be the problem. In the meanwhile I bought a VSS from Kurt (thanks!), installed it and everything works fine now!

The Dragon has speed again! :)

[GOLDCYLON]

Awesome we figured the VSS was the culprit. Glad to hear the dragon was not slayed during the process and thanks for closing out the post ;) In order to help the next member out.

[DaveK]

Glad to hear the dragon was not slayed during the process

It bit me though - always does when I work on it. These Dragons have sharp teeth and like to remind you that you're not 100% boss ;)

[rkreigh]

You got it. There is some other stuff, but the only thing worth mentioning is the coolant readout. code -16-

What fluid are you running in the trans?

Get under spray the area with some brake kleen, pull the connector off, spray out with some electrical contact cleaner.

Have you done anything with the stereo? SCV working correctly, cruise control operational?

Jeff,

thanks for all the help you provide troubleshooting

back to the avatar, kinda looks like she's about to start motor boating or looking for lost car keys

I think I know where they hid Jimmy Hoffa

YOWSA!!!=D>